How did Sir Owen Glenn's domestic violence inquiry get $7 billion figure wrong?

Domestic violence in New Zealand has a high cost. Photo / Thinkstock

Sir Owen Glenn's family violence inquiry has stumbled again, producing a $7 billion estimated cost of family violence based on the mis-reading of a key research paper.

A report by economist Suzanne Snively and Wellington theatre student Sherilee Kahui, published by the inquiry yesterday, said family violence cost New Zealand between $4.1 billion and $7 billion a year - up from Ms Snively's last estimate in 1994 of just $1 billion.

But the higher figure of $7 billion was based on a claim that 23.6 per cent of women born in Christchurch in 1977 suffered intimate partner violence in the year leading up to interviews when they were 25 in about 2002.

That figure in the original paper published in 2005 by the Christchurch Health and Development Study actually refers to the number of men as well as women who scored 3 or 4 points on a violence victimisation scale for intimate partner violence. Two-thirds of people in the study scored below 3 points and 9.4 per cent scored above 4 points.

Those scoring 3 or 4 points were described in the original paper as "predominantly a group of individuals reporting frequent minor psychological aggression and occasionally severe psychological aggression", but "none reported any of the signs of severe domestic violence [injury or fearfulness]".

The mistake is the latest of a series of misfortunes that have dogged the inquiry. Its founding director Ruth Herbert and other experts resigned last year, and most other experts left after reports that Sir Owen had faced charges of physically abusing a woman in Hawaii in 2002.

Inquiry spokeswoman Marie McNicholas declined to comment on the latest mistake and referred questions to Ms Snively. Ms Snively said the data was prepared by Ms Kahui.

Ms Kahui said the $7 billion "high-end" figure was not in an early version of the study, which initially included only the "low-end" estimate of $4.1 billion and what is now described as a "moderate scenario" of $4.5 billion.

The high-end estimate was added after experts in Auckland and Wellington said they believed the true domestic violence victimisation rates were higher than the "moderate scenario" rates of 18.2 per cent for women and 1.9 per cent for men.

"We were struggling to find empirical evidence of an estimate that would be higher than 18.2 per cent," Ms Kahui said. "So it was about finding something higher."

A 'people's report'

What is the inquiry aimed at?
Sir Owen Glenn said the inquiry would produce "an evidence-based blueprint" that could make NZ a world leader in addressing child abuse and domestic violence.

What has it achieved so far?
A "people's report" reporting what people said to the inquiry was published in June.

What's gone wrong?
Founding director Ruth Herbert and other experts resigned last year, and board member Donna Grant has taken a leave of absence. Media have reported 2002 charges against Sir Owen of allegedly physically abusing a young woman, and Sir Owen's legal battles to regain control of his money.

How will it end?
The "blueprint" is due to be published at the end of this month.

On the web: glenninquiry.org.nz